Relative Speed
SSC GD Exam Preparation - Quantitative Aptitude
Relative Speed is used when two objects move towards or away from each other.
It helps in solving problems related to trains, cars, walking persons, boats, etc.
1️⃣ What is Relative Speed?
Relative speed = difference or sum of speeds of two moving objects, depending on their direction.
Used when:
- • Two objects move in the same direction
- • Two objects move towards each other (opposite direction)
- • One object is chasing another
2️⃣ Cases of Relative Speed
✔ Case 1: Same Direction
When two objects move in same direction:
Relative Speed = Faster speed - Slower speed
👉 Because the faster one is catching up slowly.
✔ Case 2: Opposite Direction
When two objects move in opposite direction:
Relative Speed = Speed 1 + Speed 2
👉 Because the distance between them reduces quickly.
✔ Case 3: One Chasing Another
Same direction → difference of speeds
Opposite direction → sum of speeds
3️⃣ Formulae Used
➡ Time Taken to Catch or Meet
Time = Distance / Relative Speed
➡ Distance Covered During Meeting
Distance = Relative Speed × Time
4️⃣ Unit Conversion (Very Important)
✔ km/hr → m/s
Multiply by 5/18
✔ m/s → km/hr
Multiply by 18/5
🧠 15 Practice Questions (With Answers)
Test your relative speed concepts with these SSC GD level practice questions. Click on "View Answer" to check your understanding.
Q1. Two cars run in the same direction at 60 km/hr and 40 km/hr. Relative speed = ?
View Answer
= 60 − 40 = 20 km/hr
Q2. Two trains approach each other at 50 km/hr and 30 km/hr. Relative speed = ?
View Answer
= 50 + 30 = 80 km/hr
Q3. A car moving at 70 km/hr chases another at 50 km/hr. Relative speed?
View Answer
= 70 − 50 = 20 km/hr
Q4. Two persons walk towards each other at 4 km/hr and 3 km/hr. When will they meet if distance = 14 km?
View Answer
Relative speed = 7 km/hr, Time = 14/7 = 2 hours
Q5. Two bikes move away from each other at 40 km/hr and 20 km/hr. How fast is distance increasing?
View Answer
= 40 + 20 = 60 km/hr
Q6. A train (60 km/hr) meets another (40 km/hr). Time to meet if distance = 50 km?
View Answer
Relative = 100 km/hr, Time = 50/100 = 0.5 hr
Q7. A man runs at 10 km/hr chasing another at 6 km/hr. How long to catch if lead = 400 m?
View Answer
Relative speed = 4 km/hr = 4000 m/hr, Time = 400/4000 = 0.1 hr = 6 min
Q8. Two cars opposite directions at 90 km/hr & 60 km/hr. Relative speed = ?
View Answer
= 150 km/hr
Q9. A car (72 km/hr) moves behind a bus (54 km/hr). Relative speed?
View Answer
= 72 − 54 = 18 km/hr
Q10. Person A walks at 5 km/hr, B at 3 km/hr same direction. Time to meet if gap = 2 km?
View Answer
Relative = 2 km/hr, Time = 2/2 = 1 hour
Q11. A train (20 m/s) meets another train (10 m/s). Relative speed?
View Answer
= 20 + 10 = 30 m/s
Q12. Two trains running opposite direction at 50 km/hr & 25 km/hr take 10 sec to cross. Distance covered?
View Answer
Relative = 75 km/hr = 75 × 5/18 = 20.83 m/s, Distance = 20.83 × 10 = 208.3 m
Q13. A scooter 60 km/hr and a cycle 20 km/hr. Same direction. Relative speed?
View Answer
= 40 km/hr
Q14. Two trains approach at 36 km/hr & 72 km/hr. Relative speed in m/s?
View Answer
(36 + 72) × 5/18 = 108 × 5/18 = 30 m/s
Q15. A car at 80 km/hr meets another at 20 km/hr. Time to meet if distance = 50 km?
View Answer
Relative = 100 km/hr, Time = 50/100 = 0.5 hr = 30 min
✅ SSC GD Exam Strategy
🟢 Remember same direction = difference, opposite direction = sum
🟢 Practice unit conversions quickly for speed calculations
🟢 Master time and distance formulas with relative speed
🟢 Learn to identify direction of movement correctly
🟢 Time yourself - aim for 45-60 seconds per relative speed question
You've completed Relative Speed Concepts!
SSC GD Tip: Relative speed problems are very common in competitive exams. Focus on mastering the direction-based formulas - same direction uses difference of speeds, while opposite direction uses sum of speeds. Remember to convert units consistently (km/hr to m/s when needed). Practice different scenarios like trains meeting, persons chasing, and vehicles moving in different directions. Regular practice with previous year SSC GD questions will build your speed and accuracy in solving relative speed problems efficiently.
Master Relative Speed for SSC GD Exam!
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